Carcharhinus Leucas Research Articles

Bioaccumulation and biomagnification of mercury and methylmercury in four sympatric coastal sharks in a protected subtropical lagoon

Mercury bioaccumulation is frequently observed in marine ecosystems, often with stronger effects at higher trophic levels. We compared total mercury (THg) and methylmercury (MeHg) from muscle with length, comparative isotopic niche, and diet (via δ13C and δ15N) among four sympatric coastal sharks in Florida Bay (USA): blacknose, blacktip, bull, and lemon. Mercury in blacknose and blacktip sharks increased significantly with size, whereas bull and lemon sharks had a high variance in mercury relative to size. Both δ13C and δ15N were consistent with general resource use and trophic position relationships across all species. A significant relationship was observed between δ13C and mercury in blacktip sharks, suggesting an ontogenetic shift isotopic niche, possibly a dietary change. Multiple regression showed that δ13C and δ15N were the strongest factors regarding mercury bioaccumulation in individuals across all species. Additional research is recommended to resolve the mechanisms that determine mercury biomagnification in individual shark species.

Influence of Temperature, Salinity, and Dissolved Oxygen on the Stress Response of Bull (Carcharhinus leucas) and Bonnethead (Sphyrna tiburo) Sharks after Capture and Handling

ABSTRACT Hyatt, M.W.; Anderson, P.A., and O'Donnell, P.M., 2018. Influence of temperature, salinity, and dissolved oxygen on the stress response of bull (Carcharhinus leucas) and bonnethead (Sphyrna tiburo) sharks after capture and handling. Capture and handling stress can induce acidosis in sharks. This response, endured during commercial bycatch and in catch-and-release recreational fisheries, could be exacerbated in certain environmental conditions. To assess environmental influence on stress response, changes in acid-base, blood gas, and metabolite analytes (pH, pCO2, and lactate) measured with the i-STAT portable clinical analyzer were evaluated immediately after capture and removal from gillnets among wild bull (Carcharhinus leucas) and bonnethead (Sphyrna tiburo) sharks caught in waters of differing temperature (T), salinity (Sal), and dissolved oxygen (DO). Time from capture to blood collection (C-BD) was also recorded. Effects of T, Sal, DO, and C-BD on acid-base physiology were evaluated by mode...

Diet of the bull shark, Carcharhinus leucas, and the tiger shark,Galeocerdo cuvier, in the eastern Pacific Ocean

This study presents information on the diet of two shark species, Carcharhinus leucas and Galeocerdo cuvier, that inhabit the southeastern Pacific Ocean. The stomachs were collected from October 2003 to July 2005 in Ecuador. Stomachs of 41 C. leucas and six G. cuvier were analyzed. According to the index of relative importance (%IRI), the most important prey for C. leucas were fishes: family Ophichthidae (13.41%), Tylosurus pacificus (9.79%), Katsuwonus pelamis (4.54%), and fish remains (44.81%). G. cuvier, for its part, consumed squids: Ancistrocheirus lesueuri (45.14%), Pholidoteuthis boschmaii (7.81%), and Octopoteuthis spp. (5.17%), as well as turtles: Caretta caretta (9.7%), Lepidochelys cf. kempii (5%), and turtle remains (16.5%). The results show that C. leucas (trophic level, ITR; 4.32 $\pm$ 0.13) and G. cuvier (ITR; 4.26 $\pm$ 0.09) are tertiary consumers, occupying high positions in the food chain, but also are generalist predators that feed on a variety of prey. The high frequency of sea turtles in the stomachs of G. cuvier (>300 cm) suggests that this shark species is an important predator of turtles, which are commonly found along the southeastern Pacific coasts.

Energy metabolism in mobile, wild-sampled sharks inferred by plasma lipids.

Evaluating how predators metabolize energy is increasingly useful for conservation physiology, as it can provide information on their current nutritional condition. However, obtaining metabolic information from mobile marine predators is inherently challenging owing to their relative rarity, cryptic nature and often wide-ranging underwater movements. Here, we investigate aspects of energy metabolism in four free-ranging shark species (n=281; blacktip, bull, nurse, and tiger) by measuring three metabolic parameters [plasma triglycerides (TAG), free fatty acids (FFA) and cholesterol (CHOL)] via non-lethal biopsy sampling. Plasma TAG, FFA and total CHOL concentrations (in millimoles per litre) varied inter-specifically and with season, year, and shark length varied within a species. The TAG were highest in the plasma of less active species (nurse and tiger sharks), whereas FFA were highest among species with relatively high energetic demands (blacktip and bull sharks), and CHOL concentrations were highest in bull sharks. Although temporal patterns in all metabolites were varied among species, there appeared to be peaks in the spring and summer, with ratios of TAG/CHOL (a proxy for condition) in all species displaying a notable peak in summer. These results provide baseline information of energy metabolism in large sharks and are an important step in understanding how the metabolic parameters can be assessed through non-lethal sampling in the future. In particular, this study emphasizes the importance of accounting for intra-specific and temporal variability in sampling designs seeking to monitor the nutritional condition and metabolic responses of shark populations.

Capture of a one-eyed bull shark, Carcharhinus leucas (Valenciennes 1839), from the northern Gulf of Mexico

Capture of a one-eyed bull shark, Carcharhinus leucas (Valenciennes 1839), from the northern Gulf of Mexico

The effects of Biorock-associated electric fields on the Caribbean reef shark (Carcharhinus perezi) and the bull shark (Carcharhinus leucas)

Healthy coral reefs are biologically diverse and provide vital ecosystem services. However, decreasing water quality and global warming are key contributors to coral reef decline, which poses substantial environmental threats. In response to this degradation, an innovative coral reef restoration technology, called Biorock, utilizes weak direct current electric fields to cause limestone deposition on conductive materials, inevitably inducing prolific coral reef growth. Although expediting coral growth, research on how the associated electric fields may impact the behavioural patterns of teleosts and/or organisms (i.e. elasmobranchs) possessing electroreception capabilities is lacking. Therefore, we studied the behavioural responses of two shark species, the bull shark (Carcharhinus leucas) and the Caribbean reef shark (Carcharhinus perezi) and multiple teleost species towards weak direct current electric fields in Bimini, Bahamas. Generalized linear mixed model analyses based on 90 trials illustrate that both the feeding and avoidance behaviors ofC. leucasandC. pereziwere significantly associated with treatment type, with the weak experimental electrode treatments resulting in the greatest quantity of avoidances and fewest feedings for both species. However, data analyses illustrate that teleost feeding behavior was not observably impacted by experimental treatments. Although the Biorock technology exhibits promise in coral reef restoration, the findings from this study illustrate a need for future large-scale studies assessing shark behavioral patterns around these devices, since the deterrence of apex predators may impact ecosystem balance.

Inferring trends and linkages between shark abundance and shark bites on humans for shark-hazard mitigation

The present study aims at inferring linkages between the abundance of potentially dangerous sharks (PDSs) and shark hazard, so as to derive information about the underlying processes of shark peril off Recife, Brazil. Fishery-independent longline and drumline data collected from May 2004 through December 2014 for Carcharhinus leucas and Galeocerdo cuvier measuring ≥109cm were considered for analysis. Generalised additive models showed that the frequency of shark bites was directly proportional to and followed the same seasonal trends as PDS abundance, meeting the hypothesis that higher shark abundance may result in an increased chance of a shark bite. However, the species-specific seasonality of bull and tiger sharks seemed to follow distinct patterns. This method was helpful in comparing the abundance dynamics of the PDSs caught by the local shark hazard-mitigation program with the distribution of shark bites, so as to infer whether the species involved in the incidents were being effectively captured. Also, it provided some information about each species’ contribution to the overall dynamics in local shark hazard. However, despite being a potentially useful risk-management tool, its predictive efficacy for shark-peril mitigation may depend on the availability of abundant data spanning across wide temporal ranges.

New record of Carcharhinus leucas (Valenciennes, 1839) in an equatorial river system

Bull sharks are a cosmopolitan shark species frequently found in shallow shelf ocean waters and, occasionally, in several tropical river systems around the world. Due to bull shark’s capability to enter riverine systems, the documentation of its occurrence is essential for future fisheries inspections and studies. In this way, this study aims to report the presence of a medium sized specimen of C. leucas in an equatorial river system. The specimen was caught by fishermen at Mearim River, located in Northern Brazil and well known for the occurrence of tidal bores during the highest spring tides of the dry season. The event coincided with the occurrence of one of the strongest spring tides of 2015. The captured female specimen measured approximately 1300 mm and weighted 35 kg. The occurrence of this species was not known in this river basin until now. We recommend and support future ichthyologic studies in the Mearim River basin in order to provide data for the delimitation of the territory used by C. leucas in Maranhao State, specially looking into its age, growth, diet, spatial, and temporal movement patterns in this area.

Spinal deformities in free-ranging bull sharks,Carcharhinus leucas(Müller and Henle, 1839), from the western South Atlantic Ocean

Journal of Applied IchthyologyVolume 32, Issue 6 p. 1217-1220 Short Communication Spinal deformities in free-ranging bull sharks, Carcharhinus leucas (Müller and Henle, 1839), from the western South Atlantic Ocean A. S. Afonso, Corresponding Author A. S. Afonso afonso.andre@gmail.com Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilBoth authors contributed equally to this study. Correspondence André S. Afonso, Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife PE, Brazil. Email: afonso.andre@gmail.comSearch for more papers by this authorY. V. Niella, Y. V. Niella Departamento de Oceanografia, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE, BrazilBoth authors contributed equally to this study.Search for more papers by this authorE. Cavalcanti, E. Cavalcanti Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilSearch for more papers by this authorM. B. Andrade, M. B. Andrade Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilSearch for more papers by this authorJ. S. Afonso, J. S. Afonso Departamento de Medicina Veterinária, Escola Universitária Vasco da Gama, Lordemão, Coimbra, PortugalSearch for more papers by this authorP. S. Pinto, P. S. Pinto Departamento de Medicina Veterinária, Escola Universitária Vasco da Gama, Lordemão, Coimbra, PortugalSearch for more papers by this authorF. H. V. Hazin, F. H. V. Hazin Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilSearch for more papers by this author A. S. Afonso, Corresponding Author A. S. Afonso afonso.andre@gmail.com Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilBoth authors contributed equally to this study. Correspondence André S. Afonso, Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife PE, Brazil. Email: afonso.andre@gmail.comSearch for more papers by this authorY. V. Niella, Y. V. Niella Departamento de Oceanografia, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE, BrazilBoth authors contributed equally to this study.Search for more papers by this authorE. Cavalcanti, E. Cavalcanti Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilSearch for more papers by this authorM. B. Andrade, M. B. Andrade Departamento de Morfologia e Fisiologia Animal, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilSearch for more papers by this authorJ. S. Afonso, J. S. Afonso Departamento de Medicina Veterinária, Escola Universitária Vasco da Gama, Lordemão, Coimbra, PortugalSearch for more papers by this authorP. S. Pinto, P. S. Pinto Departamento de Medicina Veterinária, Escola Universitária Vasco da Gama, Lordemão, Coimbra, PortugalSearch for more papers by this authorF. H. V. Hazin, F. H. V. Hazin Departamento de Pesca e Aquicultura, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, PE, BrazilSearch for more papers by this author First published: 04 July 2016 https://doi.org/10.1111/jai.13125Citations: 5 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume32, Issue6December 2016Pages 1217-1220 RelatedInformation

Occurrence of juvenile bull sharks (Carcharhinus leucas) in the Navua River in Fiji

Effective species conservation requires the protection of all stages of its life-cycle. The Shark Reef Marine Reserve (SRMR) in Fiji is a marine protected area where large numbers of adult bull sharks (Carcharhinus leucas) congregate due to food provisioning. At the end of a calendar year bull sharks leave the area for reproductive activity, but parturition sites are still unknown. Between February 2014 and January 2015, we interviewed local fishermen and conducted a fishing survey, so as to assess presence and abundance of bull sharks in the Navua River near the SRMR. In total 84% of fishermen reported either seeing or catching sharks up to 8km upriver from the river mouth. They described them as small sharks having a rounded snout and being grey–brown in colour with a white belly, morphological characteristics that match juvenile bull sharks. During the fishing survey, a total of nine juvenile bull sharks were captured, including two that were recaptured after 108 and 92 days at liberty. Our findings confirmed the presence of bull sharks in the Navua River and provide a preliminary characterisation of a potential shark parturition or nursery area from a data-poor region.

Isolation and characterization of eight microsatellite loci from Galeocerdo cuvier (tiger shark) and cross-amplification in Carcharhinus leucas, Carcharhinus brevipinna, Carcharhinus plumbeus and Sphyrna lewini.

The tiger shark Galeocerdo cuvier (Carcharhinidae) is a large elasmobranch suspected to have, as other apex predators, a keystone function in marine ecosystems and is currently considered Near Threatened (Red list IUCN). Knowledge on its ecology, which is crucial to design proper conservation and management plans, is very scarce. Here we describe the isolation of eight polymorphic microsatellite loci using 454 GS-FLX Titanium pyrosequencing of enriched DNA libraries. Their characteristics were tested on a population of tiger shark (n = 101) from Reunion Island (South-Western Indian Ocean). All loci were polymorphic with a number of alleles ranging from two to eight. No null alleles were detected and no linkage disequilibrium was detected after Bonferroni correction. Observed and expected heterozygosities ranged from 0.03 to 0.76 and from 0.03 to 0.77, respectively. No locus deviated from Hardy-Weinberg equilibrium and the global FIS of the population was of 0.04NS. Some of the eight loci developed here successfully cross-amplified in the bull shark Carcharhinus leucas (one locus), the spinner shark Carcharhinus brevipinna (four loci), the sandbar shark Carcharhinus plumbeus (five loci) and the scalloped hammerhead shark Sphyrna lewini (two loci). We also designed primers to amplify and sequence a mitochondrial marker, the control region. We sequenced 862 bp and found a low genetic diversity, with four polymorphic sites, a haplotype diversity of 0.15 and a nucleotide diversity of 2 × 10−4.

Using an unbaited stationary video system to investigate the behaviour and interactions of bull sharks Carcharhinus leucas under an aquaculture farm

Bull sharks Carcharhinus leucas are common along the coast of Reunion Island (South-West Indian Ocean) and were suspected to aggregate in the vicinity of an aquaculture farm in Saint-Paul Bay on the west coast. In order to understand the behaviour and interaction of bull sharks near aquaculture cages at Saint-Paul Bay, we deployed an experimental unbaited stationary video camera. From 175 hours of recording during daylight hours from March to April 2012, eight individual female bull sharks (seven adults and one immature) were identified based on their natural markings. These sharks were resighted between 3 and 45 times. Residency analysis revealed site attachment under the aquaculture cages for at least three individuals over the course of the study. Recorded behaviours included intraspecific social interactions such as synchronised swimming. Social interactions and relatively strong paired associations for two pairs of females suggest some level of sociality among bull sharks around Reunion Island. Overall, our results demonstrate the utility of unbaited video systems to monitor the behaviour of adult coastal sharks.

Use of marine protected areas and exclusive economic zones in the subtropical western North Atlantic Ocean by large highly mobile sharks

AbstractStudy aim and locationMany populations of highly mobile marine fishes, including large sharks, are experiencing declines. The benefits of spatial management zones, such as marine protected areas (MPAs), for such animals are unclear. To help fill this knowledge gap, we examined core habitat use areas (CHUAs) for bull (Carcharhinus leucas), great hammerhead (Sphyrna mokarran) and tiger sharks (Galeocerdo cuvier) in relation to specific MPAs and exclusive economic zones (EEZs) in the western North Atlantic Ocean.MethodsBull, great hammerhead and tiger sharks (N = 86 total) were satellite tagged and tracked in southern Florida and the northern Bahamas between 2010 and 2013. Filtered and regularized positions from Argos locations of tag transmissions were used to generate CHUAs for these sharks. Overlaps of CHUAs with regional protected areas and exclusive economic management zones were quantified to determine the proportion of each tracked shark's CHUA under spatial protection from exploitation.ResultsA total of 0%, 17.9% and 34.7% of the regional CHUAs for tracked bull, great hammerhead and tiger sharks, respectively, were fully protected from exploitation in the study area.Main conclusionsExpansion of protected areas to include U.S. territorial waters would effectively protect 100% of the CHUAs for all tracked sharks in the study area. This finding is particularly significant for great hammerhead sharks, which are currently overfished, vulnerable to bycatch mortality and are the focus of strident regional conservation efforts. These findings also provide a means to inform decision makers and marine conservation planning efforts as to the types of management actions available and potential efficacy of spatial protections for these marine predators.

Evidence of Partial Migration in a Large Coastal Predator: Opportunistic Foraging and Reproduction as Key Drivers?

Understanding animal movement decisions that involve migration is critical for evaluating population connectivity, and thus persistence. Recent work on sharks has shown that often only a portion of the adult population will undertake migrations, while the rest may be resident in an area for long periods. Defining the extent to which adult sharks use specific habitats and their migratory behaviour is essential for assessing their risk of exposure to threats such as fishing and habitat degradation. The present study used acoustic telemetry to examine residency patterns and migratory behaviour of adult bull sharks (Carcharhinus leucas) along the East coast of Australia. Fifty-six VR2W acoustic receivers were used to monitor the movements of 33 bull sharks in the central Great Barrier Reef (GBR). Both males and females were detected year-round, but their abundance and residency peaked between September and December across years (2012–2014). High individual variability in reef use patterns was apparent, with some individuals leaving the array for long periods, whereas others (36%) exhibited medium (0.20–0.40) or high residency (> 0.50). A large portion of the population (51%) undertook migrations of up to 1,400 km to other coral reefs and/or inshore coastal habitats in Queensland and New South Wales. Most of these individuals (76%) were mature females, and the timing of migrations coincided with the austral summer (Dec-Feb). All migrating individuals (except one) returned to the central GBR, highlighting its importance as a potential foraging ground. Our findings suggest that adult bull sharks appear to be highly dependent on coral reef resources and provide evidence of partial migration, where only a portion of the female population undertook seasonal migrations potentially to give birth. Given that estuarine habitats face constant anthropogenic pressures, understanding partial migration and habitat connectivity of large coastal predators should be a priority for their management.

Patterns of Occurrence of Sharks in Sydney Harbour, a Large Urbanised Estuary.

Information about spatial and temporal variability in the distribution and abundance of shark-populations are required for their conservation, management and to update measures designed to mitigate human-shark interactions. However, because some species of sharks are mobile, migratory and occur in relatively small numbers, estimating their patterns of distribution and abundance can be very difficult. In this study, we used a hierarchical sampling design to examine differences in the composition of species, size- and sex-structures of sharks sampled with bottom-set longlines in three different areas with increasing distance from the entrance of Sydney Harbour, a large urbanised estuary. During two years of sampling, we obtained data for four species of sharks (Port Jackson, Heterodontus portusjacksoni; wobbegong, Orectolobus maculatus; dusky whaler, Carcharhinus obscurus and bull shark, Carcharhinus leucas). Only a few O. maculatus and C. obscurus were caught, all in the area closest to the entrance of the Harbour. O. maculatus were caught in all seasons, except summer, while C. obscurus was only caught in summer. Heterodontus portusjacksoni were the most abundant species, caught in the entrance location mostly between July to November, when water temperature was below 21.5°C. This pattern was consistent across both years. C. leucas, the second most abundant species, were captured in all areas of Sydney Harbour but only in summer and autumn when water temperatures were above 23°C. This study quantified, for this first time, how different species utilise different areas of Sydney Harbour, at different times of the year. This information has implications for the management of human-shark interactions, by enabling creation of education programs to modify human behaviour in times of increased risk of potentially dangerous sharks.

Behavioral Release Condition Score of Bull and Bonnethead Sharks as a Coarse Indicator of Stress

ABSTRACT Hyatt, M.W.; Anderson, P.A., and O'Donnell, P.M., 2016. Behavioral release condition score of bull and bonnethead sharks as a coarse indicator of stress. Capture and handling stress can induce acidosis and sometimes mortality in sharks. To approximate physiological condition after capture, fisheries researchers may use a behavioral health assessment at release. The goal of this study was to assess the efficacy of the behavioral release condition score (BRCS) in estimating the physiological stress response. The score was tested against changes in acid-base, blood gas, and metabolite analytes (pH, partial pressure of CO2, and lactate) and factors known to influence those analytes (species, capture and handling time, and water temperature) among wild-caught bull (Carcharhinus leucas) and bonnethead (Sphyrna tiburo) sharks. After gill net capture, sharks were processed for tagging, morphometrics, and blood sampling. Blood was sampled immediately before release. At release, a BRCS was assigned as good...

Low genetic diversity of sharks: natural patterns or induced by exploitation?

Event Abstract Back to Event Low genetic diversity of sharks: natural patterns or induced by exploitation? Fernando F. Mendonça1*, Rui Coelho2, Miguel N. Santos2, Bruno A. De-Franco1, Bruno L. Ferrette1, Millke Morales3, Juliana De-Biasi1, Sâmia M. Camargo1, Carolina Magalhães3, Claudio Oliveira3 and Fausto Foresti3 1 São Paulo Federal University, Marine Sciences, Brazil 2 Instituto Português do Mar e da Atmosfera, IPMA, Portugal 3 São Paulo State University, Morfology, Brazil Genetic diversity patterns are extremely relevant components in management plans on threatened species. However, such evaluations typically determine the current variation of this diversity without being able to characterize the magnitude of loss over the time. Considering the increasing number of sharks that have been included in the IUCN Red List of Threatened Species, without prior reviews about the molecular diversity could have been made, we present a comparison of these parameters, using sequences of the control region mitochondrial DNA of 1.016 sharks belonging to three endangered pelagic species (Carcharhinus longimanus, Alopias superciliosus and Sphyrna zygaena) and three not currently threatened (Prionace glauca, Galeocerdo cuvier and Carcharhinus leucas) from the Atlantic Ocean, of regions without signs of population genetic structure. As a result, among the endangered species was observed average nucleotide diversity π=0.00144 and haplotype Hd=0.415. Among the species not threatened such indexes were π=0.00306 and Hd=0753, 53% higher for nucleotide diversity and 45% higher for the haplotype diversity with respect to endangered species. Assessing the diversity loss of a population would imply the use of historical samples collected before population declines. However, this finding of different levels of genetic diversity in endangered species may mean that in sharks the genetic variability might not be naturally low as previously assumed, but may also be the effect of population declines due to human exploitation. Thus, the evolutionary potential of many species of sharks may become compromised even before detecting situations of population collapses. Acknowledgements Finnacial support: FAPESP 2011/23787-0 and CNPq 470762/2013 Keywords: conservation genetics, molecular diversity, endangered pelagic sharks species, control region mitochondrial DNA, Carcharhinus longimanus, Alopias superciliosus, Sphyrna zygaena, Prionace glauca, Galeocerdo cuvier, Carcharhinus leucas Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016. Presentation Type: Poster Presentation Topic: 1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS Citation: Mendonça FF, Coelho R, Santos MN, De-Franco BA, Ferrette BL, Morales M, De-Biasi J, Camargo SM, Magalhães C, Oliveira C and Foresti F (2016). Low genetic diversity of sharks: natural patterns or induced by exploitation?. Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00109 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Apr 2016; Published Online: 03 Sep 2016. * Correspondence: Prof. Fernando F Mendonça, São Paulo Federal University, Marine Sciences, Santos, SP, 11030-400, Brazil, fernandoffm@yahoo.com.br Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Fernando F Mendonça Rui Coelho Miguel N Santos Bruno A De-Franco Bruno L Ferrette Millke Morales Juliana De-Biasi Sâmia M Camargo Carolina Magalhães Claudio Oliveira Fausto Foresti Google Fernando F Mendonça Rui Coelho Miguel N Santos Bruno A De-Franco Bruno L Ferrette Millke Morales Juliana De-Biasi Sâmia M Camargo Carolina Magalhães Claudio Oliveira Fausto Foresti Google Scholar Fernando F Mendonça Rui Coelho Miguel N Santos Bruno A De-Franco Bruno L Ferrette Millke Morales Juliana De-Biasi Sâmia M Camargo Carolina Magalhães Claudio Oliveira Fausto Foresti PubMed Fernando F Mendonça Rui Coelho Miguel N Santos Bruno A De-Franco Bruno L Ferrette Millke Morales Juliana De-Biasi Sâmia M Camargo Carolina Magalhães Claudio Oliveira Fausto Foresti Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Was Everything Bigger in Texas? Characterization and Trends of a Land‐Based Recreational Shark Fishery

AbstractAlthough current assessments of shark population trends involve both fishery‐independent and fishery‐dependent data, the latter are generally limited to commercial landings that may neglect nearshore coastal habitats. Texas has supported the longest organized land‐based recreational shark fishery in the United States, yet no studies have used this “non‐traditional” data source to characterize the catch composition or trends in this multidecadal fishery. We analyzed catch records from two distinct periods straddling heavy commercial exploitation of sharks in the Gulf of Mexico (historical period = 1973–1986; modern period = 2008–2015) to highlight and make available the current status and historical trends in Texas’ land‐based shark fishery. Catch records describing large coastal species (>1,800 mm stretched total length [STL]) were examined using multivariate techniques to assess catch seasonality and potential temporal shifts in species composition. These fishery‐dependent data revealed consistent seasonality that was independent of the data set examined, although distinct shark assemblages were evident between the two periods. Similarity percentage analysis suggested decreased contributions of Lemon Shark Negaprion brevirostris over time and a general shift toward the dominance of Bull Shark Carcharhinus leucas and Blacktip Shark C. limbatus. Comparisons of mean STL for species captured in historical and modern periods further identified significant decreases for both Bull Sharks and Lemon Sharks. Size structure analysis showed a distinct paucity of landed individuals over 2,000 mm STL in recent years. Although inherent biases in reporting and potential gear‐related inconsistencies undoubtedly influenced this fishery‐dependent data set, the patterns in our findings documented potential declines in the size and occurrence of select large coastal shark species off Texas, consistent with declines reported in the Gulf of Mexico. Future management efforts should consider the use of non‐traditional fishery‐dependent data sources, such as land‐based records, as data streams in stock assessments.Received January 8, 2016; accepted August 17, 2016

A float-release package for recovering data-loggers from wild sharks

The rapidly expanding use of high-resolution data-loggers to study marine vertebrates presents a wealth of new opportunities for understanding the behavior, physiology, and ecology of these animals in situ. It also presents a number of new logistical challenges, one of the biggest of which is the need to physically recover the tag in order to acquire data, thus, a novel data-logger release and recovery package was designed and tested. This package consisted of a microsphere-resin float, very high frequency (VHF) transmitter, and galvanic timed release (GTR) device which allowed acceleration data logger (ADL) tags to remain on free-living sharks for several days before detaching from the fin. Upon release, tags floated to the surface and were located using a VHF receiver and yagi antenna. This method has been used successfully on blacktip, bull, nurse, and white sharks to produce an overall recovery rate of 95.7% on 47 deployments over periods of 1–111h and shark displacement distances up to 35km. This represents a cost-effective method for recovering data-loggers from sharks and large teleosts.

Contrasting movements and connectivity of reef-associated sharks using acoustic telemetry: implications for management.

Understanding the efficacy of marine protected areas (MPAs) for wide-ranging predators is essential to designing effective management and conservation approaches. The use of acoustic monitoring and network analysis can improve our understanding of the spatial ecology and functional connectivity of reef-associated species, providing a useful approach for reef-based conservation planning. This study compared and contrasted the movement and connectivity of sharks with different degrees of reef association. We examined the residency, dispersal, degree of reef connectivity, and MPA use of grey reef (Carcharhinus amblyrhynchos), silvertip (C. albimarginatus), and bull (C. leucas) sharks monitored in the central Great Barrier Reef (GBR). An array of 56 acoustic receivers was used to monitor shark movements on 17 semi-isolated reefs. Carcharhinus amblyrhynchos and C. albimarginatus were detected most days at or near their tagging reef. However, while C. amblyrhynchos spent 80% of monitoring days in the array, C. albimarginatus was only detected 50% of the time. Despite both species moving similar distances (< 50 km), a large portion of the population of C. albimarginatus (71%) was detected on multiple reefs and moved more frequently between reefs and management zones than C. amblyrhynchos. Carcharhinus leucas was detected less than 20% of the time within the tagging array, and 42% of the population undertook long-range migrations to other arrays in the GBR. Networks derived for C. leucas were larger and more complex than those for C. amblyrhynchos and C. albimarginatus. Our findings suggest that protecting specific reefs based on prior knowledge (e.g., healthier reefs with high fish biomass) and increasing the level of protection to include nearby, closely spaced reef habitats (< 20 km) may perform better for species like C. albimarginatus than having either a single or a network of isolated MPAs. This design would also provide protection for larger male C. amblyrhynchos, which tend to disperse more and use larger areas than females. For wide-ranging sharks like C. leucas, a combination of spatial planning and other alternative measures is critical. Our findings demonstrate that acoustic monitoring can serve as a useful platform for designing more effective MPA networks for reef predators displaying a range of movement patterns.